Amanda Seyfried has opened up about the difficulties of dating Dominic Cooper, insisting she hated knowing the British actor was shooting romantic scenes with female co-stars while they were apart.

The “Les Miserables” actress began a relationship with Cooper after they played a couple in 2008 movie musical “Mamma Mia!,” but they were often in different countries due to their busy work schedules.

Seyfried admits it was torture knowing Cooper was getting close to his female cast mates, and she still has her suspicions about rumors he cheated on her with Irish actress Ruth Negga, who is now his girlfriend.

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In a candid chat with magazine Allure, Seyfried explains, “That was hard, knowing he’s going to make out with Keira Knightley or the girl he’s now dating (Negga). I was in Ireland and the Daily Mail article came out and he was caught with his co-star.

“To this day, he says it never happened, but now they’re dating. You know what I mean? He is one of my closest friends still, but that is what’s hard about dating an actor.”

Cooper was first linked to Negga after they appeared together in West End play “Phaedra” in 2009.

Dominic Cooper has told fans that the hirsute man with the “huge package” in his new movie poster is not him.

The “Mamma Mia!” star’s head was planted on a much bigger man’s body for the provocative naked shot used on billboards for “The Devil’s Double,” in which Cooper plays both Saddam Hussein’s sadistic son Uday and an Iraqi man who was forced to act as his body double.

The poster features the actor’s character, covered in gold and sitting down with his legs wide apart.

But honest Cooper can’t have his fans believing that’s what he looks like naked.

He explains, “It’s brilliantly hideous, but it’s eye catching. There’s this bloke in the poster with a really hairy chest and a huge package and that’s certainly not me! But it is my head.”

Adriana M. Barraza / WENN Amanda Seyfried ended her “messy” on-set affair with Dominic Cooper when she discovered he had a longtime girlfriend at home – but gave the actor another chance after he flew …

Amanda Seyfried ended her “messy” on-set affair with Dominic Cooper when she discovered he had a longtime girlfriend at home – but gave the actor another chance after he flew halfway across the world to woo her.

The pair became romantically involved while they were filming movie-musical “Mamma Mia!” even though the British actor was already in a committed relationship with girlfriend of 12 years Joanna Carolan.

Seyfried admits the “overlap” was “messy” so they parted ways and she started dating someone else – until Cooper split from his girlfriend in Britain and flew to the set of her movie “Dear John” to win her back.

She tells Britain’s Glamour magazine, “We fooled around so much during the rehearsals for ‘Mamma Mia!’ But it was messy because there was some overlap with his girlfriend who he’d been with for 12 years. I didn’t know how he was going to deal with that, so we went our separate ways and I began dating someone else. Then Dominic flew over to Charleston (South Carolina) where I was filming ‘Dear John,’ and made sure I never saw that guy again.”